Numerous implantable medical devices exist today that implement a variety of detection schemes and therapies to address various cardiac arrhythmias while supporting heart function to facilitate adequate blood flow to fulfill the needs of the body's tissues. Typically, the heart loses propulsive power because the cardiac muscle loses capacity to stretch and contract. Often, the ventricles do not adequately fill with blood between heartbeats and the valves regulating blood flow may become leaky, allowing regurgitation or backflow of blood. The impairment of arterial circulation deprives vital organs of oxygen and nutrients. Fatigue, weakness, and inability to carry out daily tasks may result.
Not all cardiac patients suffer debilitating symptoms immediately. Some may live actively for years. Yet, with few exceptions, the disease is relentlessly progressive. As cardiac disease progresses, it tends to become increasingly difficult to manage. Even the compensatory responses it triggers in the body may themselves eventually complicate the clinical prognosis. For example, when the heart attempts to compensate for reduced cardiac output, it adds muscle causing the ventricles to grow in volume in an attempt to pump more blood with each heartbeat. This places a still higher demand on the heart's oxygen supply. If the oxygen supply falls short of the growing demand, as it often does, further injury to the heart may result. The additional muscle mass may also stiffen the heart walls to hamper rather than assist in providing cardiac output.
Current standard treatment for cardiac diseases is typically centered around treatment with medicine. Cardiac surgery has also been performed on a small percentage of patients with particular etiologies. Although advances in pharmacological therapy have significantly improved the survival rate and quality of life of patients, some cardiac patients are refractory to drug therapy, have a poor prognosis and limited exercise tolerance. In recent years, implantable cardiac devices, such as pacemakers and implantable cardioverter defibrillators (ICDs) have emerged as effective treatments for many patients with drug-refractory cardiac disease.
For implantable device systems, safety and ease of operation are important. In at least some known systems, a user (e.g., a physician) must program, into the implantable device prior to or during implantation, lead configurations for the implantable device based on the type of lead implanted. Further, nearly all modern cardiac implantable systems that support pacing require an external instrument a programmer) to perform the programming. Accordingly, it would be desirable to have an implantable device that is able to automatically determine pace and sense configurations to provide cardiac support to the patient with or without pre-programming, improving flexibility for the system and reducing time required for the implantation procedure.